The present invention relates to an apparatus and method for regulating the temperature of an object without the use of an external power supply.
Currently there are many materials that need to be transported that are sensitive to temperature variations. Common examples are food products, medical and chemical samples, human organs needed for transplant, as well as archeological and forensic samples. The common methods for preserving the constant temperature of transportable materials use active mechanical refrigeration, blocks of ice, thermal gels and packs, infrared reflective thermal materials and vacuum insulated flasks and other containers.
Each of these means of maintaining temperature has its own unique drawbacks. Mechanical refrigeration requires the use of heavy and cumbersome apparatus, including sealed containers, heat exchangers, and power sources. While effective at maintaining a narrow range of temperatures, it is difficult to provide a refrigeration solution that is easily portable. While there are vehicles that carry mechanical refrigeration units, these are generally larger highway vehicles and are difficult to take in to remote areas. Additionally, in order for portable mechanical refrigerators to function, they require a steady source of electricity. In the case of movable mechanical refrigerators, this power is supplied by a car or truck engine or a portable generator. Regardless of the mechanism, these power units require maintenance and fuel, and are not environmentally friendly.
Infrared reflective materials, are inefficient to the task of maintaining a temperature range. Generally they allow for some retention of the temperature range, but the design of the materials and their use results in thermal leakage.
Vacuum flasks operate by providing an inner and outer container while a sealed vacuum space is located between them. The vacuum space operates as an insulator preventing the transmission of thermal energy. In practice, the vacuum containers tend to be inefficient at maintaining temperature and are difficult to shape into a variety of container forms.
Known prior art portable cooling apparatuses are disclosed for example in U.S. Pat. No. 4,530,220 to Nambu et al. The respective disclosures are therein are incorporated by reference.
U.S. Pat. No. 4,530,220 to Nambu et al. discloses a deformable bag for use as a cooling medium. Nambu places small thermal gel pieces in a deformable bag so that they are able to migrate around the interior volume of the deformable bag. The bag is made of a flexible polyethylene or like material. The thermal gel pieces are of industry standard composition, however, they are provided in smaller than average pre-cast blocks. Upon use of the device in Nambu, the small blocks and flexible material conform to the rough dimensions of the material to be cooled. Nambu clearly is superior to the previously mentioned portable temperature maintaining apparatus. However there are clear drawbacks from using a device as described in Nambu. Both the natural ice and thermal compounds are unable to maintain their temperature within a narrow time range. In the example of Nambu, the smaller than average pre-cast blocks will have a large total surface area (when compared to the surface area of the thermal battery envisaged by the present invention), and will lose temperature more rapidly After a short period of time, the effectiveness of the overall material has been reduced. Furthermore, as they begin to warm, the ice or gel packs undergo dimensional transitions that decrease their direct contact with the object to be cooled. Therefore, what is needed is a method and apparatus that allows for an object to have prolonged contact with a portable cooling block.
Another difficulty with natural ice or a thermal battery is the fact that upon freezing, the thermal battery or the natural ice expands, but on losing cold, it will retract to its original shape and dimension. This makes it difficult to construct a suitable container for these items that will hold them securely whilst accommodating this change. If a container is made using the non-frozen dimensions of a thermal battery, it becomes difficult to construct a housing that will secure a frozen thermal battery due to unpredictable expansion. On the other hand, if the container is constructed according to expanded dimensions, upon the battery losing cold and retraction to its original unexpanded form and dimensions, extra space would result which may create a gap between the thermal battery and the goods to be stored thus losing intimate and regular contact, which will affect the transfer of cold temperature from the thermal battery to the goods. Therefore, what is needed is an apparatus that allows for a container and a thermal battery to be fitted securely despite the deformation process, so that there is continued contact between the thermal battery and the object needed to be kept within the temperature range.
The present invention proposes a method of maintaining a pre-set temperature range for objects over a long period of time without requiring an electrical power source. This is accomplished by making a thermal battery of special construction which is made by filling a specially designed housing with thermal gel or compound which can be pre-set at certain temperatures i.e. a thermal battery. Additionally, the present invention proposes an apparatus that ensures constant contact across the surface area of a thermal battery housing with either a thermal conductor or an object in need of a constant, pre-set temperature.